In systems that incorporate the use of rotating drive shafts, it is often necessary to have data indicative of the torque and speed of the shafts in order to control the same or other devices associated with such rotatable shafts. Accordingly, it is desirable to detect and measure torque in an accurate, reliable, and inexpensive manner. The ability to detect and measure the torque imposed on rotating shafts is a critical parameter in application such as, for example, automotive vehicles.
SAW sensors can be utilized in a variety of sensing applications, such as torque, pressure and/or temperature detection. Such sensors can be implemented, for example, by locating a SAW device on an etched diaphragm within a piezoelectric material such as, for example, quartz. In automotive vehicles, the SAW sensor package can be mounted on an automobile flex plate for sensing the torque. The flex plate, analogous to a flywheel, generally connects the torque converter to an engine crankshaft in a vehicle with an automatic transmission.
The majority of prior art SAW sensor elements are packaged in a machined steel case or a ‘button’ or ‘pill’ component. The package of a typical SAW sensor includes two parts—a base portion upon which metallic pins can be glass fritted and a flat disc that functions as a lid for the case or enclosure. Once the SAW device is placed inside the case, a wire-bonding process can electrically connect the pins to the sensor element, following which, the lid can be assembled and permanently joined to the base utilizing, for example, a laser welding process. Thereafter, the SAW sensor package can be joined to a surface of a mechanical component, whose torque is to be measured, by bonding the package to the component utilizing an adhesive or laser welding methodology.
Such an approach requires that the sensor package, along with the mechanical component, be held together for either the welding process or the adhesive curing process. Hence, fixtures and machinery are required for handling large and/or heavy mechanical components, which may increase processing costs for handling and high temperature curing, due to the presence of a larger mass. Similarly, laser welding of the button sensor package to the flex plate requires the development of an improved welding process because the two materials that are to be joined may be very different, with respect to welding. Consequently, the heat generated during a welding operation is capable of damaging the sense die and the heat-affected zone (HAZ) of the weld circle and can act as a damper with respect to the effective transfer of strain to the sensor. Also, the button is typically made of steel and constitutes a machined component, which increases production costs. A solution to these problems is to produce the button by metal injection molding; however, the change in the material properties of the material after manufacture is unknown.
Based on the foregoing, it is believed that a need exists for an improved method and/or system for packaging and mounting SAW sensor element(s) for use in a variety of applications such as, for example, automobile flex plate applications. Such an approach is described in greater detail herein.